Power delivery and data communication over a single pair of cables

ABSTRACT

Systems and methods are disclosed for an integrated circuit (IC) comprising an oscillator, an on-off-keying modulator configured to modulate input data coupled to the oscillator, a serial communications transmitter coupled to the on-off-keying modulator, a serial communications receiver coupled to the serial communications transmitter by a set of cables, and an envelope detector coupled to the serial communications receiver. In the IC, power and data are simultaneously delivered across the same set of cables from the serial communications transmitter to the serial communications receiver.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/684,243, filed Jun. 13, 2018, which is hereby incorporated byreference.

BACKGROUND

A typical system for RS485/RS422 data communication needs two pairs ofcables whenever power delivery is also required. This additional cablingresults in higher costs and may be disadvantageous from a coststandpoint.

SUMMARY

Systems and methods are disclosed for an integrated circuit (IC)comprising an oscillator, an on-off-keying modulator configured tomodulate input data coupled to the oscillator, a serial communicationstransmitter coupled to the on-off-keying modulator, a serialcommunications receiver coupled to the serial communications transmitterby a set of cables, and an envelope detector coupled to the serialcommunications receiver. In the IC, power and data are simultaneouslydelivered across the same set of cables from the serial communicationstransmitter to the serial communications receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1 illustrates system in which power is transmitted through separatecables from RS485/RS422 data.

FIG. 2 illustrates an example in which power and data signals aretransmitted through the same pair of cables.

FIG. 3 illustrates an example of the system architecture of the system.

FIG. 4 illustrates an example of a block diagram of the system.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a system in which power is transmittedthrough separate cables from RS485/RS422 data. RS-485 applicationsbenefit from differential signaling over twisted-pair cables. Asdiscussed herein, RS485 and RS422 are industry standards defining theelectrical characteristics of drivers and receivers for use in serialcommunications. RS485 defines the electrical characteristics of driversand receivers that could be used to implement a balanced multipointtransmission line. See “The RS-485 Design Guide,” available athttps://www.ti.com/lit/an/slla272c/slla272c.pdf. Typically, RS485 andRS422 standards involve data transmission only and do not contemplatepower delivery through the same physical medium. This type of cabling isgenerally at a system level and does not incorporate any kind of signalmodulation. In the system shown, sub-system A 110 is coupled tosub-system B 140 using two pairs of cables. The first set of cables 120,120′ couple the Power IN 112 of Sub-system A 110 to the Power OUT 142 ofSub-system B 140. In this manner, power is delivered from Sub-system B140 to Sub-system A 110. Separately, data is transmitted from Sub-systemA 110 to Sub-system B 140 using a second pair of cables 130, 130′ thatcouple the RS485/RS422 data transmitter 114 to the RS485/RS422 datareceiver 144. The system of FIG. 1 thus requires two sets of cables foroperation, thereby resulting in significant cabling costs andunfavorable weight increases in implementation.

FIG. 2 illustrates an example in which power and data signals aretransmitted through the same pair of cables. Compared to the example ofFIG. 1, the example of FIG. 2 discloses superior techniques for datatransmission, preferably using the RS485 and/or RS422 protocols. Theillustrative system shown in FIG. 2 comprises Sub-system A 210 andSub-system B 230. Analogously to FIG. 1, power is delivered and data istransmitted between Sub-system A 210 to Sub-system B 230. Sub-system Acomprises a power input, Power IN 211, and a RS485/RS422 datatransmitter 212. Sub-system B comprises a power output, Power OUT 231,and a RS485/RS422 data receiver 232. Sub-system A 210 and Sub-system B230 are coupled together via a single pair of cables 220, 220′.

In FIG. 2, the single pair of cables 220, 220′ is configured to carryboth power and data. Power delivery may include an alternating current(AC) voltage or direct current (DC) voltage. In this example, datatransmission utilizes any suitable protocol such as the RS485 or RS422protocols. Power is delivered from Sub-system B 230 to Sub-system A 210from the power output 231 to the power input 211 via the single pair ofcables 220, 220′. The power input 211 is coupled to the single pair ofcables 220, 220 through a first pair of coupling inductors 213 and 213′,respectively. Analogously, the power output is coupled to the singlepair of cables through a second pair of coupling inductors 233 and 233′,respectively.

The single pair of cables 220, 220′ also carry data transmission betweenthe RS485/RS422 data transmitter 212 and the RS485/RS422 data receiver232. As data is transmitted, it passes through the AC couplingcapacitors 214 and 234 in the first cable 220, and through the ACcoupling capacitors 214′ and 234′ through the second cable 220′. Thefirst cable 220 and the second cable 220′ are connected by a firstresistor 216 on the RS485/RS422 data transmitter 212 side and a secondresistor 236 on the RS485/RS422 data receiver 232 side.

As shown in FIG. 2, data is transmitted between the RS485/RS422 datatransmitter 212 and the RS485/RS422 data receiver 232 over the singlepair of cables 220, 220′. In this illustrative implementation, data ismodulated over the existing power cabling. As will be explained furtherherein, the modulation may take the form of on-off-keying (OOK)modulation. In certain implementations, that OOK modulation may behandled inside of an RS485 transceiver. In practice, because the OOKmodulation occurs inside the transceiver, there is a broad market forthe technology. That is because the system offers a wide data range inoperation, there is no data DC balancing required, and the electricalsignaling parameters conform to the TIA/EIA-485A standard. Furthermore,because OOK modulation occurs in the transceiver, there are nocontroller or software updates required. Thus, the hardware of thedescribed examples may be included as part of a larger system withoutcostly and time-consuming modifications.

The implementation of FIG. 2 also offers all of the attendant benefitsof the RS485 standard because it uses the RS485 physical layer, so thatthere is flexibility in its implementation. Furthermore, in certainimplementations, the system incorporates SSC operations to reduce EMI,thereby improving system performance. In certain other implementations,the system is implemented in a master-slave architecture, allowing forreal-time/deterministic operation.

FIG. 3 illustrates an example of the system architecture. In FIG. 3,data is input at Data IN 302. A representation of the data is shown asthe waveform 303 below the diagram. The data modulated by an oscillator304 and the OOK modulator 306 prior to being transmitted to the RS485driver (also referred to as the transmitter) 308, which is connected tothe RS485 receiver. The data transmitted to the RS485 driver 308 has amodulated waveform 305. The data that is input into the RS485 driver 308is then further modified in accordance with the RS485 standard, suchthat the data waveform 307 (top waveform) that travels through the pairof cables 310, 310′. On each cable 310, 310′, the data passes through afirst set of AC coupling capacitors 312, 313 on the first cable 310 anda second set of AC coupling capacitors 312′, 313′ on the second cable310′.

Data transmission preferable utilizes the RS485 or RS422 protocols.Power is delivered from the power output, Power OUT 316, to the powerinput, Power IN 314, via the single pair of cables 310, 310′. The powerinput 314 is coupled to the single pair of cables 310, 310′ through afirst pair of coupling inductors 315, 315′, respectively. Analogously,the power output, Power OUT, 316 is coupled to the single pair of cablesthrough a second pair of coupling inductors 317 and 317′, respectively.Further, as in FIG. 3 above, the pair of cables 310, 310′ are connectedby a first resistor 318 on the RS485 driver 308 side and a secondresistor 318′ on the RS485 receiver 320 side. A graphical representationof the power delivery through the pair of cables 310, 310′ is shown inthe waveform 307 (bottom waveform) below the cables 310, 310′.

At the RS485 receiver 320, the data signal is isolated once more fromthe power delivery and transmitted to the envelope detector 322 as awaveform 321. That waveform is further modulated at the envelopedetector 322, such that the data output, Data OUT, 324 may take the formof the data output signal 323.

FIG. 4 illustrates an example block diagram of the system. Theintegrated circuit (IC) 400 includes an RS485 half-duplex system withtime division multiplexing. An RS422 standard may be substituted incertain implementations. The IC 400 provides for on-off-keyingmodulation of the data input within the RS485/RS422 transceiver. Theshaded components of the chip 400, OSC 404, Mod. 406, and Env. Det. 422,correspond to the oscillator 304, the OOK modulator 306, and theenvelope detector 322, described in FIG. 3. The unshaded components ofthe chip 400 are found in implementations of the RS485 standard. Thosecomponents, which correspond to those described in FIG. 3, are the datainput, D 402, the RS485 transmitter/driver, TX 408, the first and secondresistors 418, 418′, the RS485 receiver, RX 420, and the data output, R424. Additionally, the chip diagram of FIG. 4 shows the input buffer 403and the output buffer 423, which are also found inside the RS485transceiver. The chip 400 components operate consistently with how theyare described in FIG. 3.

In a use of the chip 400, the data input 402 flows into the input buffer403, which then transmits the data to the modulator 406. The datamodulated by an oscillator 404 and the OOK modulator 406 prior to beingtransmitted to the RS485 driver 408, which is connected to the RS485receiver 420. In this example, the RS485 driver 408 is coupled to a fastdischarge circuit (FDC) 410. The FDC 410 actively drives the RS-485 busto the output common mode voltage with zero swing. This circuit 410guarantees deterministic discharging of the external series capacitorsand extends the cable reach of the system. The RS485 driver 408 and theRS485 receiver 420 are coupled together with a pair of cables 410, 410′.As described in FIG. 3, the pair of cables 410, 410′ are connected by atleast one resistor 418, 418′ on each side. The cables 410, 410′ are alsocoupled to a first bus pin 444 and a second bus pin 446, through whichthe chip 400 can deliver power, which may be inductively coupled, acrossthe cables 410, 410′. The chip's 400 architecture also preferablyincludes supply voltage 442, a ground 448, a receiver enable 450, and adriver enable 452.

Modifications are possible in the described systems and methods, andother implementations are possible, within the scope of the claims. Allreferences cited herein are expressly incorporated in their entireties.

In describing the examples in the drawings, specific terminology will beresorted to for the sake of clarity. However, the examples are notintended to be limited to the specific terms so selected, and it is tobe understood that each specific term includes all technical equivalentsthat operate in a similar manner to accomplish a similar purpose.Several examples are described for illustrative purposes, but theprinciples described herein may be embodied in other forms notspecifically shown in the drawings. In this description, the term“couple” or “couples” means either an indirect or direct wired orwireless connection. Thus, if a first device couples to a second device,that connection may be through a direct connection or through anindirect connection via other devices and connections.

What is claimed is:
 1. An integrated circuit comprising: an oscillatorhaving an oscillator output; an on-off-keying modulator having a datainput, having an input coupled to the oscillator, and having a modulatedoutput; a serial communications transmitter having an input coupled tothe modulated output and having a first transmitter output and a secondtransmitter output; a serial communications receiver having a firstreceiver input coupled to the first transmitter output, having a secondreceiver input coupled to the second transmitter output, and having areceived data output; an envelope detector having an input coupled tothe received data output and having a data output; a first bus terminalcoupled to the first transmitter output and adapted to be capacitivelycoupled to a first communication cable that is inductively coupled to apower circuit; and a second bus terminal coupled to the secondtransmitter output and adapted to be capacitively coupled to a secondcommunication cable that is inductively coupled to the power circuit. 2.The integrated circuit of claim 1, in which the serial communicationstransmitter and the serial communications receiver implement the RS485standard.
 3. The integrated circuit of claim 1, including a resistorcoupling together the first bus terminal and the second bus terminal. 4.The integrated circuit of claim 1, including an input buffer having anoutput coupled to the data input.
 5. The integrated circuit of claim 1,in which the serial communications transmitter has a fast dischargeinput and including a fast discharge circuit having an output coupled tothe fast discharge input.
 6. The integrated circuit of claim 1, in whichthe integrated circuit is a half-duplex system.
 7. A data communicationssystem comprising: (a) a transceiver including: a first bus terminal, asecond bus terminal, a data input, and a data output; an on-off-keyingmodulator having an input coupled to the data input and having amodulated output; a serial communications transmitter having an inputcoupled to the modulated output and having outputs coupled to the firstbus terminal and the second bus terminal; and a serial communicationsreceiver having inputs coupled to the first bus terminal and the secondbus terminal and having an output coupled to the data output; (b) afirst capacitor having a first terminal coupled to the first busterminal and having a second terminal; (c) a second capacitor having afirst terminal coupled to the second bus terminal and having a secondterminal; (d) a first inductor having a first terminal coupled to thesecond terminal of the first capacitor and having a second, powerterminal; and (e) a second inductor having a first terminal coupled tothe second terminal of the second capacitor and having a second, powerterminal.
 8. The data communications system of claim 7, in which a powercircuit is coupled to the second, power terminals of the first inductorand the second inductor.
 9. The data communications system of claim 7,including a resistor coupling the first bus terminal to the second busterminal.
 10. The data communication system of claim 7, in which theserial communications transmitter complies with the RS485 standard. 11.The data communications system of claim 7, in which the system isconfigured to use electrical signaling parameters that conform to theTIA/EIA-485A standard.
 12. A method for data transmission comprising:providing modulated data from an on-off-keying modulator in response toreceiving input data; transmitting the modulated data from a serialcommunications transmitter to first and second bus terminals;capacitively coupling with first capacitors the first and second busterminals to a twisted pair cable; capacitively coupling with secondcapacitors the twisted pair cable to third and fourth bus terminals;inductively coupling power from a first power circuit to the twistedpair cable between the first capacitors and the twisted pair cable;inductively coupling power from the twisted pair cable to a second powercircuit between the second capacitors and the third and fourth busterminals; and providing received data in response to the transmittedmodulated data from a serial communications receiver coupled to thethird and fourth bus terminals.
 13. The method of claim 12, includingproviding output data from an envelope detector having an input coupledto the received data.
 14. The method of claim 13, including modulatingthe received data at the envelope detector.
 15. A communications systemcomprising: (a) one twisted pair of cables, the cables having first endsand opposed second ends; (b) a first sub-system including: a transmittercircuit having first and second bus terminals; first capacitors couplingthe first and second bus terminals of the transmitter circuit to thefirst ends of the cables; a first power circuit having first and secondpower terminals; and first inductors coupling the first and second powerterminals to the first ends of the cables at points between the firstcapacitors and the first ends of the cables; and (c) a second sub-systemincluding: a receiver circuit having third and fourth bus terminals;second capacitors coupling the third and fourth bus terminals of thereceiver circuit to the second ends of the cables; a second powercircuit having third and fourth power terminals; and second inductorscoupling the third and fourth power terminals to the second ends of thecables at points between the second capacitors and the second ends ofthe cables.
 16. The system of claim 15 in which the transmitter circuitis a RS495/RS422 data transmitter circuit and the receiver circuit is aRS495/RS422 data receiver circuit.
 17. The system of claim 15 in whichthe first sub-system includes an on-off-keying modulator having anoutput coupled to an input of the transmitter circuit.
 18. The system ofclaim 15 in which the first power circuit is a power in circuit and thesecond power circuit is a power out circuit.